The present invention relates to a machine for converting rolled cloth, consisting of a fabric or of any other material, for example plastic, into sheets.
As is known, sheet-making machines are used for stacking fabrics or other materials initially arranged in roll form. These machines, in fact, have a surface for storing the sheets to be stacked and a mobile carriage which is located on the said storage surface and supplies the fabric or similar material to be stacked. The distance traveled by the mobile carriage, which performs alternating movements, determines the width of the sheets to be stacked.
Previous studies by the same applicant have already led to the development of a particularly efficient sheet-making machine with many advantages, owing, in particular, to a loading device designed to position and automatically unwind a roll. This loading device comprises, in fact, forked levers designed to hold and move a bar about which a said roll revolves, as well as unwinding means and conveyor belt means which can be directly engaged by the roll, the axial bar of which is inserted between the forked levers. In practice, during unwinding the roll is held so as to be substantially free and rest against the conveyor belt means, which ensure that the fabric or similar material to be stacked is unwound in a precise manner. It must also be added that the abovementioned forked levers can be swung up so as to transfer automatically the rolls from a loading station to the abovementioned conveyor belt means.
This sheet-making machine has proved to be completely satisfactory. However, it has been noted that the same machine needs to be improved further with regard to the devices which control the speed at which the fabric or similar material is fed onto the said stacking surface.
In fact, it is known that, in order for the sheets of cloth to be arranged precisely on top of each other during unrolling, the speed at which the cloth itself is fed must be identical to the speed at which the mobile carriage performs the alternating translatory motion. Only in this manner can the fabric or similar material which is supplied be prevented from slipping horizontally with respect to the stacking surface and precise stacking be achieved.
The currently available devices for controlling the fabric feed rate are unsatisfactory for various reasons.
Some of these devices consist of two bars rotatable about a middle axis of rotation located between the same. The said bars give an S-shaped trajectory to the fabric. This device is useful, in particular, for tensioning initially the cloth during unwinding, but cannot be employed effectively to correct any errors in the speed at which the cloth is fed.
There are other devices where the rollers around which the fabric or similar material is partially wound during unwinding are each driven by an associated motor and where at least one of these motors has a variable speed which can be set by means of special controls. With these devices, the presence of an operator who is able to use the said controls is always required.
Finally, control devices are known which are able to determine the degree of tensioning the fabric or similar material being stacked and automatically adjust the motors which control the feed movement of the fabric itself.
These devices are also somewhat unsatisfactory since they do not allow continuous adjustment of the speed at which the cloth is unwound, but only partial and in any case substantially imprecise adjustment thereof.
The sheet-making machine already designed by the same applicant has been able to use, until now, known devices for controlling the feed rate of the fabric, thanks to the precision of the already mentioned loading device, which partly compensates for the deficiencies of the control devices since it avoids, from the outset, many irregularities in the way the cloth is fed. However, as is obvious, if an efficient and satisfactory device for controlling the fabric feed rate were to be developed and applied to the said sheet-making machine, it would mean that the sheet-making machine itself would operate with an exceptional degree of precision in all situations.
The general object of the present invention is precisely to design a machine for converting rolled cloth into sheets, of the type already developed by the same applicant, which also has an efficient and advantageous device for controlling the feed rate of fabric or similar material to be stacked. Within the scope of this general object, an important object of the present invention is to design a sheet-making machine with a control device which has a simple structure and can be easily applied to the machine itself at a low cost and with a minimum of inconvenience.
These objects and others which will emerge more clearly below are substantially achieved by a machine for converting rolled cloth into sheets, comprising at least a surface for stacking the sheets of fabric or similar material and a mobile carriage located on the said stacking surface and provided with a loading device designed to position and automatically unwind a roll, the said loading device comprising in particular forked levers designed to hold and move an axial bar of the said roll as well as unwinding means and conveyor belt means with which the said roll can be directly engaged, the said machine having a device for controlling the fabric feed rate, which device comprises a bar transverse to the direction in which the said fabric is fed and held oscillatably; by the said carriage in a position tending to form a hollow in the fabric itself, and a speed regulator which is able to detect the oscillations of the said bar and is designed to control a variable-speed electric motor which causes the said fabric to be fed.